1. Field of the Invention
The present invention relates to a lumbar support device for use in a vehicle seat such as an automotive seat.
2. Description of Prior Art
Among various lumbar support devices provided in a vehicle or automotive seat and operable to adjustably support the lumbar part of an occupant sitting on the seat, there has been known such type of lumbar support device provided on a seat frame, wherein a lumbar plate is connected to one end of a torsion bar, and an adjustment element, such as a cam having discrete surfaces, is connected to another end of the same torsion bar, and wherein an operation lever is fixed to that adjustment cam, such that the lumbar plate member may be displaced in a direction toward and away from the occupant's lumbar part at a desired lumbar support position by rotational operation of the lever. A typical example of this sort of lumbar support device is disclosed from the Japanese Laid-Open U.M. Pub. No. 62-52457.
However, the conventional lumbar support devices, including that Japanese prior-art lumbar support device, has been found troublesome or inefficient in assembling its plural constituent elements or members together into a resulting lumbar support device, in view of the fact that the connection of the torsion bar to the lumbar plate and seat frame requires separate connecting elements or an additional step for machining or bending some local portions of the torsion bar subsequent to the same torsion bar being located or provisionally secured via support brackets on the lumbar plate and seat frame. This is also true with respect to the mounting of the cam in a cam support bracket fixed on the seat frame. Consequently, under this hitherto state of art, the assembly process is slow and cumbersome and requires an increase the number of separate connecting elements.